Some aspects of plant and research experience in the use of new high strength martensitic steel P91 (original) (raw)
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New 12%Cr-steel for tubes and pipes in power plants with steam temperatures up to 650°C
Materials at High Temperatures, 2006
Nowadays, high efforts are undertaken to increase efficiency and thereby minimizing harmful emissions of power plants. This can be achieved by increasing the steam temperature and pressure to supercritical conditions. Presently martensitic 9% Cr-steels, e.g. P91, E911 and P92 are used for power plants with advanced steam parameters. While these materials have the highest creep rupture strength values of ferritic steels, their oxidation resistance is lower than 12% Cr-steels, such as X20CrMoV12-1. With increasing steam temperature (target: 650°C) the lifetime of components made of 9% Cr-steel becomes limited not only by creep but also by oxidation.
Development of creep-and corrosion-resistant steels for future steam power plants
Reliable energy supply is -among many others -one of the most important requirements modern industrial societies are based on. The scheduled transition in energy policy towards renewable sources postulates a reduction of Germany's energy needs by about 10 % [UBA] until 2050, but future scenarios nevertheless predict an increase in global energy demand for the upcoming decades. Moderate economic growth in the OECD countries, but especially the rapidly growing economies of the non-OECD countries, may cause an almost tripled global energy demand by 2050 [Shell]. Having in mind the environmental impact of energy supply and the need for valuable primary resource conservation efficient and sustainable technologies for energy conversion are required. Although renewable energy technologies are of great interest fossil fuels will continue to play a major role in future energy supply security. Due to decreasing availability of fossil fuels, its increasingly cost intensive exploitation, the fact that large amounts of CO2 are emitted in combustion whose separation from power plant exhaust gases may cause a loss of overall plant efficiency of about 10 -25 % [Metz] system efficiency will play the leading role in resource conservation, cost saving and environmental protection. Improved plant efficiency, however, requires increased process temperatures and pressures and can therefore only be reached by improved materials.
High strength and heat resistant chromium steels for sodium-cooled fast reactors
2004
This report provides the results of a preliminary phase of a project supporting the Advanced Nuclear Fuel Cycle Technology Initiative at ANL. The project targets the Generation IV nuclear energy systems, particularly the area of reducing the cost of sodium-cooled fast-reactors by utilizing innovative materials. The main goal of the project is to provide the nuclear heat exchanger designers a simplified means to quantify the cost advantages of the recently developed high strength and heat resistant ferritic steels with 9 to 13% chromium content. The emphasis in the preliminary phase is on two steels that show distinctive advantages and have been proposed as candidate materials for heat exchangers and also for reactor vessels and near-core components of Gen IV reactors. These steels are the 12Cr-2W (HCM12A) and 9Cr-1MoVNb (modified 9Cr-1Mo). When these steels are in tube form, they are referred to in ASTM Standards as T122 and T91, respectively. A simple thermal-hydraulics analytical model of a counter-flow, shell-and-tube, oncethrough type superheated steam generator is developed to determine the required tube length and tube wall temperature profile. The single-tube model calculations are then extended to cover the following design criteria: (i) ratio of the tube stress due to water/steam pressure to the ASME B&PV Code allowable stress, (ii) ratio of the strain due to through-tube-wall temperature differences to the material fatigue limit, (iii) overall differential thermal expansion between the tube and shell, and (iv) total amount of tube material required for the specified heat exchanger thermal power. Calculations were done for a 292 MW steam generator design with 2200 tubes and a steam exit condition of 457°C and 16 MPa. The calculations were performed with the tubes made of the two advanced ferritic steels, 12Cr-2W and 9Cr-1MoVNb, and of the most commonly used steel, 2¼Cr-1Mo. Compared to the 2¼Cr-1Mo results, the 12Cr-2W tubes required 29% less material and the 9Cr-1MoVNb tubes required 25% less material. Also, with the advanced steels, the thermal strains in the tubes and differential thermal expansion between tubes and shell were significantly better. For steam generators with higher steam exit temperatures, the benefits of the advanced steels become much larger. A thorough search for the thermal and mechanical properties of the two advanced steels was conducted. A summary of the search results is provided. It shows what is presently known about these two advanced steels and what still needs to be determined so that they can be used in nuclear heat exchanger designs. Possible follow up steps are outlined.
High-Temperature Degradation and Protection of Ferritic and Austenitic Steels in Steam Generators
Journal of Materials Engineering and Performance, 1998
The useful life of superheaters and reheaters of power stations which use heavy fuel oil is shortened and their continuous service is inhibited by corrosion (fireside) and creep-type problems. The increase of corrosion attack on boilers is caused by the presence of fuel ash deposits containing mainly vanadium, sodium, and sulfur which form low-melting-point compounds. The tubes are exposed to the action of high stresses and high temperatures, producing the so-called "creep damage." In this work, two kinds of results are reported: lab and field studies using a 2.25Cr-1Mo steel. The laboratory work was in turn divided into two parts. In the first, the steel was exposed to the action of natural ash deposits in oxidant atmospheres at 600 °C for 24 h. In the second part, tensile specimens were creep tested in Na 2 SO 4 , V 2 O 5 , and their mixture over a temperature range of 580 to 620 °C. In the field work, components of a power station were coated with different types of nickel-and iron-base coatings containing chromium, Fe-Cr, and Fe-Si using the powder flame spraying technique. After testing, the coated tubes were analyzed using electron microscopy. The results showed that all the coating systems had good corrosion resistance, especially those containing silicon or chromium.
Materials for ultra-supercritical coal-fired power plant boilers
2006
The efficiency of conventional fossil power plants is a strong function of the steam temperature and pressure. Research to increase both has been pursued worldwide, since the energy crisis in the 1970s. The need to reduce CO 2 emission has recently provided an additional incentive to increase efficiency. The main enabling technology in achieving the above goals has been the development of stronger hightemperature materials. Extensive R&D programs have resulted in numerous high strength alloys for heavy section piping, and tubing needed to build boilers. The study reported here is aimed at identifying, evaluating and qualifying the materials needed for the construction of the critical components of coal-fired boilers capable of operating with 760 1C (1400 1F)/35 MPa (5000 psi) steam. The economic viability of such a plant has been explored. Candidate alloys applicable to various ranges of temperature have been identified. Stress rupture tests have been completed on the base metal and on welds to a number of alloys. Steamside oxidation tests in an autoclave at 650 (1200 1F) and 800 1C (1475 1F) have been completed. Fireside corrosion tests have been conducted under conditions simulating those of waterwalls and superheater/reheater tubes. Weldability and fabricability of the alloys have been investigated. The capability of various overlay coatings and diffusion coatings have been examined. This paper provides a status report on the progress achieved to date on this project.
Materials Science and Engineering: A, 2009
The goal of developing new heat resistant 11%Cr ferritic-martensitic steels with sufficient creep and oxidation resistance up to 650 • C was pursued within a joint project following an alloying concept based on physical metallurgy principles. The highest creep strength combined with good oxidation resistance was achieved for a Ta-alloyed test melt (11 wt.% Cr, W, Co, Mo, V, 0.09 wt.% Ta, relatively high contents of C and B). The microstructural evolution during creep was investigated by transmission electron microscopy for the Ta-alloyed melt in comparison to a sister melt where Ta was exchanged for 0.04%Nb. It is proposed that fine particles of types MX and M 23 C 6 (M: metallic element, X: interstitial elements) are the cause of the outstanding creep resistance of the Ta-alloyed melt.
Lessons from the past: materials-related issues in an ultra-supercritical boiler at Eddystone plant
Materials at High Temperatures, 2007
Electricity fuels the engine of technological progress, and so there is little dispute that the manner in which electrical power is generated in the coming years will affect all of our lives in ways both obvious and subtle. There will be economic effects that will dictate, for example, how much it costs to heat homes and run computers, and there will be environmental effects that will influence the quality of the resources available to sustain life. A dispute arises, however, in determining how best the power can be produced, since the relative sensitivity to the potential effects, be they economic or environmental, varies substantially among the many interested parties. Regardless of sensitivities, there is broad agreement that electric power must remain inexpensive, both to maintain the extraordinary standard of living achieved by the materially developed nations and, at least as importantly, to sustain the progress of developing nations toward equitable levels of prosperity. With abundant, inexpensive power as a primary goal for future generators, certain conclusions inevitably follow. Among these is the fact that for many parts of the world, including both the US and China, coal will remain an essential fuel in the production of electric power because it is plentiful, relatively cheap, and its supply secure. The reference to China is particularly significant, because China is in the midst of a massive construction effort that will add tens of thousands of megawatts of new coal-fired generating capacity in the next ten years, and there is every reason to expect that other developing countries will soon follow suit. There is enormous potential, therefore, to minimize the impact of this massive influx of capacity on the global environment, through an improvement in the overall efficiency of coal-fired boilers. The task for the worldwide power industry, therefore, is clear: improve the efficiency of coal-fired power plants to levels consistent with the best existing engineering technology. But what are those levels? The existing fleet of sub-critical coal-fired steam plants typically operate at efficiencies in the range of 32-34% (based on HHV). Recent units built in Europe and Japan have been designed to run at steam conditions that achieve a significant improvement in efficiency, approaching 40% (HHV). Major research efforts in both the US and Europe have made substantial progress toward the development of coal-fired ultra-supercritical steam generators that will operate at efficiencies approaching 50% based on HHV. A component test facility designed to evaluate operation of major steam generator components at 700 C (1292 F) will soon be operational in Germany, and the first demonstration plant incorporating advanced ultra-supercritical technology could be constructed as soon as the year 2010. With this ambitious schedule in mind, the question posed by those who will be responsible for the operation of these new ultra-supercritical power plants is obvious: will they perform reliably under the conditions of flexible operation that are likely to be imposed by modern de-regulated markets? The real intent of this question is more subtle: do the materials and methods of construction exist to build these advanced coal-fired boilers. In large part, the answer to that question lies in a US power plant located not far from the Philadelphia airport. The plant is Exelon's (formerly the Philadelphia Electric Company) Eddystone plant. The steam generator for Unit 1 at that plant, which was designed and built by Combustion Engineering (now ALSTOM Power, Inc.) in the 1950s, has operated successfully for more than 44 years at steam conditions more advanced than any other coal-fired unit in operation today. This paper will briefly review salient features of the operating history of Eddystone 1, focussing on the materials-related problems that forced a modest retreat from the original and unprecedented design conditions, but emphasizing, as well, the record of many years of reliable operation at very aggressive steam conditions. It will then discuss a few of the more significant materials-related issues involved in operating a steam generator at Eddystone-like conditions as a
2016
Reduction in CO2 emissions from coal-fired power plants is one of the major challenges in order to decrease global warming effect. In energy sector, the aim to reduce CO2 emission can be achieved by increasing the operating temperature (and pressure) of water steam system, which results in an increase in overall coal fired power plant efficiency. Currently the main components of coal fired power plants are made from the materials designed years ago; to meet harsh eco criteria such materials are not suitable for harsh conditions of modern coal-fired power plant. Subcritical power stations are main contributor in CO2 emission globally, with high CO2 emission and low efficiency ~ 37 %. The next-gen coal-fired power plants have potential to reach 55% efficiency, taking into account, that 1% increase in absolute efficiency results in as much as 3% reduction in CO2 emissions, 55 % of CO2 lower emission achieved. Modern, advanced coal fired power stations operating under Ultra Super Critic...
Improved Austenitic Steels for Power Plant Applications
2002
Using alloy design principles, an austenitic alloy, with base composition of Fe-16Cr-16Ni-2Mn-1Mo (in weight percent, wt%), was formulated to which up to 5 wt% Si and/or Al were added specifically to improve the oxidation resistance. Cyclic oxidation tests were carried out in air at 700 and 800°C for 1000 hours. For comparison, Fe-18Cr-8Ni type-304 stainless steel alloys was also tested. The results showed that at 700°C, all the alloys were twice as oxidation resistant as the type-304 alloy (i.e., the experimental alloys showed weight gains about half that of type-304). Surprisingly, at 800°C, alloys that contained both Al and Si additions were less oxidation resistant than the type-304 alloy. However, alloys containing only Si additions were significantly more oxidation resistant than the type 304 alloys (i.e., showed weight gains 4 times less than the type-304 alloy). Further, alloys with only Si additions pre-oxidized at 800°C, showed zero weight gain in subsequent testing for 1000 hours at 700°C. This implies the potential for producing in-situ protective coating for these alloys. Preliminary exposure tests (1%H 2 S at 700 o C for 360 hrs) indicated that the Si-modified alloys are more sulfidation resistant than type-304 alloy. The mechanical properties of the alloys, modified with carbide forming elements, were also evaluated; and at 600, 700 and 800 o C the yield stresses of the carbide modified alloys were twice that of type-304 stainless steel. In this temperature range, the tensile properties of these alloys were comparable to literature values for type-347 stainless steel. It should be emphasized that the microstructures of the carbide forming alloys were not optimized with respect to grain size, carbide size and/or carbide distribution. Also, presented are initial results of vari-strain weld tests used to determine parameters for joining these alloys.
International Journal of Pressure Vessels and Piping, 2004
The paper presents high temperature mechanical properties and non-destructive evaluation (NDE) of chromium-molybdenum (Cr-Mo) ferritic steels widely used as structural materials for steam generator (SG) applications. Creep and low cycle fatigue deformation and damage (the important design considerations for SGs) of ferritic steels are presented. Recent trend and advances in ferritic steels for SG applications are discussed. The paper also highlights the recent results obtained on creep and fatigue properties of indigenously developed steels. Weld and weld joints of ferritic steels are known to be the weak links affecting the life of the components. The creep properties of weld joints are presented. Apart from mechanical behaviour of ferritic steels, the paper deals with some of the recent results on the characterisation of microstructural features such as grain size, nucleation and growth of secondary phases, degradation of microstructure due to thermal ageing and creep, and assessment of creep and fatigue damage of ferritic steels using advanced NDE techniques.